Heat screen control for motion picture projectors



May 11, 1948.

H. N. FAIRBANKS HEAT SCREEN CONTROL FQR MOTION PICTURE PROJECTORS Filed March 9, 1946 4, 35 3 as 2 0 l4 A 37'.* "37a m I5 350 3340 39 34 I3 3| 32 I6 FIG 3 INVENTOR v HENRY N. FAIRBANKS ATTORNEYS a circumferential groove 31 in shaft l4. As here shown balls 36 are carried in radial openings 38 in member 33 and are pressed inwardly by a circular spring clip 39 which surrounds the formation of balls and lies in a circumferential groove 40 in member 33. In the position of the parts shown in Fig. 2 clutch member 33 and its friction disk 34 are held away from the face of gear 13 so that the gear, and the film movement ll are not driven.

By forcibly shifting lever 35 in a direction indicated by the arrow the spring detent balls 35 are forced out of groove 31 and, clutch member 33 moving toward the right in Fig. 2, the balls enter another shaft groove 31a as friction disk 34 is pressed against gear I3 and gear I3 is pressurally confined between that friction disk and the other friction disk 3|. Groove 31a is so positioned that when disk 34 is in full pressural contact with gear l3, balls 36 have not quite fully entered inwardly into groove 31a but engage only the left hand side of that groove; so that the inward spring pressure acting on the balls tends to press clutch member 33 toward the right and to maintain the frictional pressure upon the driving gear. Continuing frictional pressure need not be maintained by clutch actuating lever 35; and in both the open and closed positions of the clutch lever 35 may merely loosely engage in clutch groove 3511..

As here shown, and preferred for simplicity, collar 32 is fixed rotatively to shaft H but clutch element 33 is not. Either one or both of 32 and 33 may be rotatively fixed to the shaft. And triction disks 3! and 34 may be afilxed either to the gear 13, or to 32 and 33, or may float between the gear and elements 32 and 33.

The cooperating interconnection between clutch mechanism 30 and the heat screen 20 may be of various types. It is here shown in the form of an arm 45 which is connected to clutch lever 35 to move with it. Such an interconnecting arm may move either pivotally or slidingly, depending upon the physical relationship of lever 35 and heat screen 29, and the physical relationship of their planes of movement. In the schematic drawings,- the planes of movement of lever 35 and heat screen 20 are illustrated as being parallel, and the interconnecting arm 45 is therefore shown as being a simple sliding arm or rod, connected at one end at 46 to lever 35 and at its other end (Fig. 1) shown as sliding through a guide 41 and having its end in stop relationship to an edge of arm 23 of the heat screen. In the illustrated positions of the parts, with clutch 30 open and the film movement not being driven, the end of arm'45 lies close to or against the left hand edge of heat screen arm 23, preventing the heat screen from being moved by the air current to the dotted line position of Fig. 1. Upon closure of the movement driving clutch, the movement of lever 35 and arm 45 toward the left removes the stop restriction on heat screen arm 23 and thus, without positively moving the heat screen to its dotted line position to expose thefilm or the aperture, allows the heat screen then to be moved to its film exposing position by air circulation set up by fan #6. Thus, if the projector operator should close clutch'30 before starting the driving motor and then, with the source of illumination turned on, start the film in motion by starting the driving motor, the heat screen will not be moved to its film exposing position until the driving motor and fan i 6 have substantially reached operating speed; as the heat screen is so weighted by vane 2401 otherwise as to remain in its film protecting- 4 position until the air current impelled by fan it reaches substantially its operating velocity.

The clutch mechanism in and of itself is not the subject matter of the invention claimed herein. Although here described in preferred specific form, the clutch mechanism is merely illustrative of means for drivingly connecting the film movement to the driving motor, or of means for driving the movement. That driving is pre!- erably, of course, from the same motor that drives the fan.

I claim:

1. In a motion picture projector mechanism, which embodies structure having a film exposure aperture, 8. film movement, a driving motor and an air circulating fan driven from the motor; the combination of a shiftable heat screen having a. normal position overlying the exposure aperture and shiftable to non-overlying position by virtue of flow of the fan impelled air current when the fan is driven at normal speed, a clutch mechanism through which the film movement is driven from the shaft, and a movable screen stop member connected with the clutch mechanism and movable therewith as the clutch mechanism opens and closes, said stop member lying in a position to prevent movement of the heat .screen from its normal position when the clutch mechanism is open and moving to a position allowing movement of the heat screen when the clutch mechanism is closed.

2. In a motion picture projector mechanism,

which embodies structure having a film exposure aperture, a film movement, a driving motor and an air circulating fan driven from the motor; the combination of a shiftable heat screen having a. normal position overlying the exposure aperture and shiftable to non-overlying position by virtue of flow of the Ian impelled air current when the fan is driven at normal speed, means through which the film movement is driven from the motor, said means embodying a motor driven shaft, a movement driving gear loosely mounted on the shaft, a longitudinally shiftable clutch element on the shaft adapted in one position to drivingly engage the gear and in another position to disengage the gear, yielding detent means for holding said clutch element in either of its positions, a clutch element shifting lever; and a movable stop member connected with the lever and lying in a position stopping heat screen movement from its normal position when the clutch' element is in its gear disengaging position and moving to a position where it allows the heat screen to be moved by fan impelled air flow when the clutch element engages the gear.

3. In a motion picture mechanism which embodies structure having a film aperture, means for circulating a stream of cooling air past the aperture, a film movement, and movement driving means by which the movement may be driven; the combination of a shiftable heat screen having a normal position overlying the exposure aperture and shiftable by virtue of flow of the stream of coolin air to a non-overlying position, and releasable screen holding means operatively connected to the film movement driving means, adapted to prevent movement of the heat screen from its normal position when the film movement is not being driven, and'releasable to allow such:

which embodies structure having a film exposure aperture, a 111m movement, a driving motor and an air circulating fan driven irom the motor and adapted to circulate a stream or cooling air past the aperture; the combination of a shiitable heat screen having a normal position overlying the exposure aperture and shiftable to non-overlying position by virtue of flow of the fan impelled air current, means for drivingly connecting the film movement with the driving motor, and means actuated by said connecting means and acting to prevent the shifting of the heat screen by the 10 air current when said connecting means is inoperative and the movement is not drivingly connected with the motor.

HENRY N. FAIRBANKS.

REFERENCES CITED The following references are of record in the file of this patent:

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